Insulative electrical terminal

ABSTRACT

An insulative electrical terminal is disclosed. The terminal includes a ceramic body metallized on one end which is brazed to a terminal post structure to which an electrical circuit component is to be soldered. The other end of the ceramic insulator body is affixed to a metallic chassis via a thermally conductive adhesive which preferably forms a fillet between the insulator body and a pocket formed in the metallic chassis member.

United States Patent Curtis Eugene Ward 11486 Miller Ave., Los Altos,Calif. 94022 [21] Appl. No. 848,985

[22] Filed Aug. 11, 1969 [45] Patented Nov. 2,1971

[72 Inventor [S4] INSULATlVE ELECTRICAL TERMINAL 4 Claims, 2 DrawingFigs.

[52] U.S. Cl 339/112, 174/166, 339/1 19, 339/275 [51] 1nt.Cl H01r 9/06[50] Field of Search 339/119, 112, 93 C, 275,278,198.3,218;174/153,166.l

[5 6] References Cited UNITED STATES PATENTS 2,726,280 12/1955 Demurjian174/166 2,823,251 2/1958 Clark 174/153 2,918,521 12/1959 Abrams. 174/166X 3,261,396 7/1966 Trunk. 165/80 2,836,807 5/1958 Goodfellow et al339/l98.3

Primary Examiner- Richard E. Moore Attorneys-Stanley 2. Cole and GeraldL. Moore ABSTRACT: An insulative electrical terminal is disclosed. Theterminal includes a ceramic body metallized on one end which is brazedto a terminal post structure to which an electrical circuit component isto be soldered. The other end of the ceramic insulator body is afflxedto a metallic chassis via a thermally conductive adhesive whichpreferably forms a fillet between the insulator body and a pocket formedin the metallic chassis member.

INVENTOR.

CURHS E] WARD BY ATTORNEY I l INSULATIVE ELECTRICAL TERMINAL DESCRIPTIONOF THE PRIOR ART Heretofore, electrically insulative terminals have beenemployed wherein a metallic terminal post structure, to which theelectrical component is to be soldered, is affixed to one end of ahollow ceramic body by crimping. A metallic stud is crimped to the otherend of the ceramic body. The stud screws into a threaded bore in ametallic chassis from which the component is to be supported. Some ofthe problems with this terminal are that the crimped joints made to theceramic insulator body tend to loosen as the terminal is putthroughatypical thermal cycle, such as that encountered during soldering of theelectrical component to the terminal, moreover, such crimped joints havea relatively poor thermal conductivity due to the very small thermalcross section of their line and point contacts. In addition, the hollowcentral portion of the ceramic insulator body provides an uninspectableelectrical flashover or leakage path inside the insulator. The centralbore is required in order to make the crimped joint between the solderterminal and the insulator body.

In another prior art electrically insulative terminal, the metallicterminal post structure, to which the electrical component is to besoldered, is molded into one end of a solid plastic body such as Alkyd,phenolics and the like. The problem with the molded plastic body is thatthe plastic material has a relatively poor thermal conductivity, as of0.00l cal. per gram per centimeter per degree Centigrade per second. Ina typical example, such an insulated terminal, in normal operation, canresult in a temperature drop across the insulator of approximately 60 C.This is a relatively high thermal gradient to exist across the terminaland it is desired to produce an electrically insulative terminal whichhas substantially improved thermal conductivity to the chassis.

SUMMARY OF THE PRESENT INVENTION The principal object of the presentinvention is the provision of an improved electrically insulativeterminal for electrical circuit components.

One feature of the present invention is the provision of an electricallyinsulative terminal having a ceramic insulator body with a metallicterminal post structure to which the electrical component is to besoldered being brazed to the insulator body by means of a relativelythermal-conductive metalto-ceramic fused metallic joint, whereby thethermal conduc tivity of the insulative terminal is substantiallyimproved.

Another feature of the present invention is the same as the precedingfeature wherein the ceramic insulator body is joined to a metallicchassis member by means of a thermally conductive adhesive.

Another feature of the present invention is the same as the precedingfeature wherein the end of the insulator body which is joined to themetallic chassis member is disposed within a pocket in the chassismember with a thermally conductive adhesive forming a fillet and fillingthe space within the pocket between the inside wall of the pocket andthe end of the insulator body.

Another feature of the present invention is the same as any one or moreof the preceding features wherein the ceramic insulator body is made ofa material selected from the group consisting of alumina and beryllia.

Other features and advantages of the present invention become apparentupon perusal of the following specification taken in connection with theaccompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view, partly brokenaway and partly in section of a prior art insulative electrical terminalas mounted to a chassis member, and

FIG. 2 is a view similar to that of FIG. 1 depicting the insulativeelectrical terminal of the present invention.

2 DESCRIPTION OF THE PREFERRED EMBODIMENTS per. degree Centigrade persecond. A turret-type terminal post structure 4, as of brass, is affixedto one end of the insulator 3 by being molded into the end of theinsulator body 3. A metallic stud 5 is afiixed to the other end of theinsulator body 3 by being molded into the other end of the insulatorbody 3. The stud 5 includes a threaded extension 6 threadably matingwith the internal threads of a bore 7 in the chassis plate 2.

In a typical example of the prior art insulated terminal I,-theinsulator body 3 has a length of 0.10 inch, and a diameter of 0.14 inch.The typical temperature drop across the insulator body, for theaforecited dimensions and assuming 0.l watt input at the turret terminal4 is approximately 60 C. Thus, a temperature rise of 60 C. is obtainedonly due to the poor thermal conductivity of the insulator body and thisdoes not take into account the relatively poor thermal conductivityobtained through the joints to the insulator body 3.

Referring now to FIG. 2, there is shown an insulative electricalterminal 11 incorporating features of the present invention. Insulatedterminal 11 includes a solid ceramic body member 12 to which metallicmembers maybe brazed. A suitable ceramic material for insulator 12includes ceramics, such as fosterite, steatite, alumina and beryllia.Fosterite and steatite have thermal conductivities of 0.008 and 0.006cal.

per gram per centimeter per degree Centigrade per second,

the end thereof to receive the terminal structure 13. A suitablemetallizing layer is formed by the conventional molybdenum manganesemetallizing technique. The terminal post structure 13 is then brazed bymeans of a conventional silver/copper eutectic brazing alloy material tothe metallized layer, thereby forming a metal-to-ceramic joint 14 offused metal having relatively high thermal conductivity and largethermal cross section. A circuit component 15 such as a diode, resistor,inductor, etc., has a lead thereof 16 soldered to terminal poststructure 13.

The other end of the insulator body 12 is disposed in a cylindricalrecess or pocket 17 in the chassis plate 2. A fillet of thermallyconductive adhesive such as Delta Bond 152" adhesive obtained fromWakefield Engineering of Wakefield, Mass, fills the space between theend of the insulator body 12 and the inside wall of the pocket 17 toprovide a relatively highly thermally conductive joint between theinsulator body 12 and the chassis plate 2. The aforementioned conductiveadhesive has a relatively high coefficient of thermal conductivity, asof 0.002.

Although the preferred embodiment has the insulator body disposed withina recess or pocket 17 in the chassis plate 2, this is not a requirementand as an alternative the adhesive may be disposed between the surfaceof the chassis plate 2 and the end of the insulator body 12. However,the recess 17 has the additional advantage of providing a locating holefor location of the various terminal insulator members 11.

The advantage of the insulated terminal II as compared to the prior artis that the thermal conductivity through the terminal is substantiallyimproved compared to the prior art,

thereby facilitating thermal conduction cooling of the devices connectedto the insulated terminal. More particularly, for an insulator body 12of the same dimensions as that previously cited for insulator 3, atemperature drop across insulator body 12 for 0.1 watt applied to theterminal 13 is 7.6 C. for fosterite, 10.1 C. for steatite, 1.2 C. foralumina, and 03 C. for beryllia, whereas 60 C. was obtained for Alkyd ofthe prior art.

Since many changes could be made in the above construction and manyapparently widely different embodiments of this invention could be madewithout departing from the scope thereof, it is intended that all mattercontained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

lclaim:

l. in an electrical insulative terminal for connecting circuitcomponents to a metallic chassis, means forming a ceramic insulatorbody, means forming a metallic terminal post structure afflxed to afirst end of said insulator body for connection to a circuit componentto be insulatively supported from the metallic chassis which is to bedisposed at the second end of said insulator body, THE IMPROVEMENTCOMPRISING, a metal-to-ceramic fused metallic joint disposed in betweenthe first end of said ceramic body and said terminal post for bondingsaid metallic terminal post to said ceramic insulator body, whereby arelatively high thermal conductivity path is provided from said terminalpost structure to the metallic chassis through said metal-to-ceramicmetallic joint and said insulator body and further including a metallicchassis from which the electrical component is to be supported via theintermediary of said insulator body and terminal post, said chassisincluding a recessed pocket, said second end of said insulator bodybeing disposed in said pocket, and means for supporting said insulatorbody within said pocket in thermally conductive relationship with thewalls of said pocket.

2. The apparatus of claim 1 wherein said ceramic insulator body is madeof a material selected from the group consisting of fosterite, steatite,alumina, and beryllia.

3. The apparatus of claim 1 wherein said ceramic insulator body is madeof a material selected from the group consisting of alumina andberyllia.

4. The apparatus of claim 1 wherein said means for supporting saidinsulator body comprises a thermally conductive adhesive filling thespace between the walls of said pocket and the second end of saidinsulator body.

1. In an electrical insulative terminal for connecting circuitcomponents to a metallic chassis, means forming a ceramic insulatorbody, means forming a metallic terminal post structure affixed to afirst end of said insulator body for connection to a circuit componentto be insulatively supported from the metallic chassis which is to bedisposed at the second end of said insulator body, THE IMPROVEMENTCOMPRISING, a metal-to-ceramic fused metallic joint disposed in betweenthe first end of said ceramic body and said terminal post for bondingsaid metallic terminal post to said ceramic insulator body, whereby arelatively high thermal conductivity path is provided from said terminalpost structure to the metallic chassis through said metal-to-ceramicmetallic joint and said insulator body and further including a metallicchassis from which the electrical component is to be supported via theintermediary of said insulator body and terminal post, said chassisincluding a recessed pocket, said second end of said insulator bodybeing disposed in said pocket, and means for supporting said insulatorbody within said pocket in thermally conductive relationship with thewalls of said pocket.
 2. The apparatus of claim 1 wherein said ceramicinsulator body is made of a material selected from the group consistingof fosterite, steatite, alumina, and beryllia.
 3. The apparatus of claim1 wherein said ceramic insulator body is made of a material selectedfrom the group consisting of alumina and beryllia.
 4. The apparatus ofclaim 1 wherein said means for supporting said insulator body comprisesa thermally conductive adhesive filling the space between the walls ofsaid pocket and the second end of said insulator body.